1. Technical Field
The present invention relates to an image forming apparatus and an image forming method.
2. Description of Related Arts
There has been developed an image forming apparatus capable of coping with various types of papers such as a long paper (for example, a roll-to-roll paper) wound in a roll shape or a so-called label paper attachable as a seal as well as a generally used paper having an A4 size, a B5 size, etc.
When an image is printed in an image forming apparatus by using such a special paper, material of a paper may project from the end portion of the paper. For example, when an image is printed on a label paper including an adhesive such as a paste, the adhesive may project from the end portion of the paper. Particularly, in a secondary transfer unit of an image forming apparatus employing an intermediate transfer scheme, since a label paper is brought into press-contact with an intermediate transfer belt, it is probable that an adhesive projects from the end portion of the paper, and is transferred to and is attached to the intermediate transfer belt. Furthermore, when the label paper is long, since a part including the adhesive is long, it is more probable that the adhesive is transferred and attached to the intermediate transfer belt.
Furthermore, for example, when a long paper such as a roll-to-roll paper has been cut, cutting waste may be attached to the end portion of the paper. It is probable that the cutting waste attached to the end portion of the paper is peeled off and is attached to an intermediate transfer belt.
When the adhesive, the cutting waste, etc., are transferred and attached to the intermediate transfer belt, for example, a primary transfer unit, a secondary transfer unit, and a cleaning device associated with these units may be abnormally worn, or failure may occur when a toner image is transferred.
In this regard, a technology, which has a purpose of preventing the attachment of an adhesive to a photoreceptor with respect to a label paper including the adhesive in an image forming apparatus employing a direct transfer scheme, is disclosed in Japanese Unexamined Publication No. 2004-226824. In the technology of Japanese Unexamined Publication No. 2004-226824, after an external additive having a polarity opposite to toner is supplied, the separate external additive not attached to a toner surface is allowed to be attached to a non-image area of a photoreceptor so as to be developed, and is allowed to be interposed between the paper and the photoreceptor, so that the adhesive is prevented from being attached to the photoreceptor.
However, since the amount of particles of the separate external additive not attached to the toner surface is small, the amount of particles of the external additive attached to the non-image area of the photoreceptor is also small. As a consequence, there is a problem that the effect of preventing the adhesive from being attached to the photoreceptor is small. The present invention is intended to solve the aforementioned problems, and one of the objectives of the present invention is to provide an image forming apparatus and an image forming method, by which it is possible to more reliably prevent a foreign matter projecting from the end portion of a paper from being attached to a member of a transfer unit.